def dist(x1, y1, x2, y2):
    return ((x2 - x1)**2 + (y2 - y1)**2) ** 0.5

x1, y1, x2, y2 = map(float, input().split())
print(dist(x1, y1, x2, y2)) def dist(x1, y1, x2, y2):
    return ((x2 - x1)**2 + (y2 - y1)**2) ** 0.5 dist return ((x2 - x1)**2 + (y2 - y1)**2) ** 0.5 ((x2 - x1)**2 + (y2 - y1)**2) ** 0.5 (x2 - x1)**2 + (y2 - y1)**2 (x2 - x1)**2 x2 - x1 x2 x1 2 (y2 - y1)**2 y2 - y1 y2 y1 2 0.5 x1 x1 y1 y1 x2 x2 y2 y2 x1, y1, x2, y2 = map(float, input().split()) x1 map(float, input().split()) map float input().split() ().split () input split y1 x2 y2 print(dist(x1, y1, x2, y2)) print dist(x1, y1, x2, y2) dist x1 y1 x2 y2 x1, y1, x2, y2 = map(float, input().split()) map(float, input().split()) x1 def dist(x1, y1, x2, y2):
    return ((x2 - x1)**2 + (y2 - y1)**2) ** 0.5 def dist(x1, y1, x2, y2):
    return ((x2 - x1)**2 + (y2 - y1)**2) ** 0.5 dist x2, y2 = map(float, input().split()) map(float, input().split()) x2 y1, x2, y2 = map(float, input().split()) map(float, input().split()) y1 y2 = map(float, input().split()) map(float, input().split()) y2
def dist(x1, y1, x2, y2):
    return ((x2 - x1)**2 + (y2 - y1)**2) ** 0.5

x1, y1, x2, y2 = map(float, input().split())
print(dist(x1, y1, x2, y2))
